74_5.0L_Z

I angled my radiator forward as part of an overall philosophy for handling the air that enters the front of the car. I want every air molecule that enters an opening in the front of the car to have a purpose. That is, air entering the front of the car should either cool something or feed the engine. In my case, the forward angle of the radiator allows me to establish ducting before and after the radiator that should reduce the drag coefficient of the car, increase the cooling efficiency, and possibly create a little downforce. The angle of the radiator is only part of the package. For the angle of the radiator to have any meaning, several other things have to happen: The ducting ahead of the radiator must cleanly slow the air (expand) to the face of the radiator. The ducting ahead of the radiator must be sealed to the face of the radiator (I use a rubber gasket). The ducting behind the radiator must reaccelerate the air back into the free stream. It took a lot of effort to establish the radiator ducting on my car. To do so, I designed my front frame rails so that the radiator could sit low and be unobstructed. The frame section that normally crosses in front of the radiator has been moved back in line with the sway bar. The placement of every component on the front of the engine was performed with the intention of keeping the exit plane of the radiator open. The alternator was moved to the bottom, the belt tensioner was kept as low as possible, and the radiator hoses were routed to the sides. It takes a lot of planning to do this right. If you are not planning to attend to all of the details that make the forward angled radiator beneficial, then you would be better off spending the time to assure that the radiator is sealed to the radiator support. The angle of the radiator means nothing unless the other details are in place.

While I was finalizing the design of my front end, I did a little bit of research. One of the best references that I found was a web site about cooling wankel powered aircraft. The author of the web page (Paul Lamar ) has since removed the content from the web and published a book with the content. The web page that links to the author is here: http://www.rotaryeng.net/how-to-cool12.html The web page and the book that sprang from it are a great compilation of data that sprang from research on cooling piston engine powered fighter aircraft at the end of World War Two. This book does a great job of summarizing the information from Kucheman and Weber's "Aerodynamics of Propulsion", and from London and Kay's "Compact Heat Exchangers". The book explores (among other things) two different but equally effective philosophies of inlet and outlet ducting. Kucheman and Weber's research led to a long inlet with a small front inlet that expanded smoothly until it got to the face of the radiator, and an exit that contracted as the ductwork merged with the body. Kays and London's design had the radiator laying nearly flat with a wedge shaped inlet. Both designs sought to slow the incoming air to create a high pressure region across the entire face of the radiator. Additionally both design philosophies accelerate the air in the exit duct to minimize drag. If I were to do mine again, I would probabbly lay my radiator down even further to more fully approach the London and Kays design. In fact, I would arrange it such that the top of the radiator was even with the top of the bumper and just behind it. If you are serious about designing a cooling system, read Paul Lamar's book.

My radiator is installed as in example 1. It has been tilted forward 48 degrees, and the bottom has been moved back to just forward of the sway bar. The radiator is completely sealed to the opening in the air dam wit ha rubber gasket. All air that enters the radiator exits through the hood.

Cary, I looked at the effect of chassis rake. I can raise the magic number by about half a point by lowering the rear roll center ~.75 inch. Unfortunately, my rear tires get pretty darn close to the wheel housing as it is. Additionally, going lower also forces me to have more static negative camber in the rear (I am at the limit of adjustment of my camber plates). So I decided not to lower the rear any further and to make a new front sway bar. Additionally, I think the stiffer front sway bar will help keep the inside rear tire on the ground going into the corners.

I've run a couple of events since Sebring. At Sebring, the surface was concrete and the traction was amazing. The traction was so good that the car was easy to catch if it started to oversteer or understeer. The other surfaces that I have to run on are not nearly as good. BCC in Palm Bay is smooth asphalt and has probably 80% of the grip as Sebring. The surface at the Deland airport is old deteriorated asphalt and the traction is probably 50% of Sebring. The car as I had it set-up in Sebring and most recently at Deland had a Magic Number of 2.92 per the Weight Transfer Worksheet. The car set up with a number this low should be very prone to oversteer when the power is applied coming out of the corners. At Sebring, the traction was so good that it was easy to compensate, and the car wiggled through the slalom sections amazingly well. At Deland, the car was nearly undrivable. The car was always on the hairy edge of wanting to spin, and forget accelerating out of the corners. It was not fun at all. To try and make the car more drivable on the surfaces with less traction, I am putting together a new front sway bar. The current bar is a modified stock sway bar from a coupe (18mm). I am replacing it with a modified bar from a 2+2 (20mm). According to the WTW, the magic number with the new bar should be about 4.95. The higher number should give the car a little more understeer tendency and allow me to get out of the corners a little better. In addition to the two sway bars that I've mentioned, I have a 25mm front sway bar at my disposal. The problem with a bar that big is that my Magic number would be 12.44%. A number this big would mean that the car has a strong tendency towards understeer. Anyways, with three sway bars at my disposal, I need to do some testing at the next practice day. The next practice day is coming up August 16. I plan to arrive with the 20mm bar installed, and then based on the car's performance switch to either the 18mm bar or the 25mm bar.

Most importantly, you need a clear understanding of how you intend to use the car. Will it be strictly a street car? Will it be strictly a drag car? Are autocross and track days in your future? If the car is going to be used for anything but strictly drag racing then you probably want to get rid of the C4 transmission. The C4 has no overdrive and will make the car unpleasant to drive on the highway (unless you like 3200 rpms at 70 mph). You need to have a realistic understanding of the limits of your budget and time. Building a HybridZ requires a fair amount of money and lots of time. Most builds (assuming sufficient funds) require about 1 to 2 years to complete. During the course of the build, you will reach points where the amount of work left to be completed is overwhelming. It will be tempting to give up. At the same time, there will be other demands on your time and money. You will never finish a building a project like this if the Z is not VERY high on your priority list. It sounds like your brother is a fellow gear head. If so, this may be an opportunity for some serious brotherly bonding. If you have friends that are willing to spend time with you on this project, then everything will be easier. As I've stated above, there are a lot of hurdles to clear when undertaking a project like this, but the end result is worth it. If you take your time and do it right, the completed car will be an enormous source of pride and accomplishment (and fun). Good luck and remember that there is a lot of information on this website. Most of the questions have been asked and answered. If you search and can't find the answer, then feel free to post a question.

My car has 6 degrees of caster. To achieve that, my lower ball joint is about 1" in front of the pivot for the lower control arm (in the side view). Looking down on the car from above, the control arm is angled forward ~ 5 degrees. If I were using the delrin aluminum bushings at the inner pivot, then I would not be able to push the control arm forward in that manner without applying a heck of a lot of force to the control arm, T/C rod, and the aluminum bushing. Additionally, the T/C rod is attached to the control arm with two bolts. As designed, the T/C is angled (~37 degrees) so that it is aligned with the holes in the frame and the holes in the control arm within a small range of suspension adjustment. As you push the control arm forward, the bolts at the control arm end will not line up properly. With a little effort, you would probably be able to force everything into alignment, but this creates strain on the control arm, T/C rod, and the attaching hardware. My solution was to install spherical bearings at the lower control arm pivots, and to reengineer the T/C rod to allow angle change between the control arm and T/C rod. When you get finished with that and can crank in some caster, the tire will be pushed forward in the wheelwell like this.

Unless you have spherical bearings installed at the inner pivot of the lower control arm, you should not attempt to lengthen the T/C rod. If you still have rubber at the inner pivot, you can get away with it (sort of), but if you have the common aluminum delrin adjuster the DON'T DO IT.

I'm sold on the limiters. Since finishing the suspension mods and getting new tires, I have run two autocross events. The first was at Gainesville on an asphalt track with no limiters, and the second was at sebring on concrete with the droop limiters installed. The transient response at Sebring seemed faster. I meant to disconnect the droop limiters at Sebring to get a more apples to apples comparison, but I was having so much fun that I forgot. I still haven't taken the time to fully understand why they work (at least not formally). Subjectively, I like the way the car handles with the limiters installed. Objectively, I plan to do back to back runs with and without them installed at the next practice event.

Thanks Jon, I am really happy with it. I love the way the car now wiggles through the slalom sections. I noticed the front tire coming up but not the rear. I'll have to look a little closer at the video. The concrete looks so washed out because the temperature was 97*F that day. I'll borrow a camera soon and get some pictures of the limiters.

A little update: I ended up replacing my tires with the same size (245/45/16) Hoosier A6. I wanted to go up a size, but my old tires became corded before I could acquire some larger wheels. Even though I couldn't go to the next larger size, I have to say this: New Hoosiers are MAGIC! My old tires had died from age and heat cycling, so I had enough time to forget what they should feel like. The car does what I tell it to, when I tell it to almost without exception. I just wish the driver was a little better. Additionally, I have installed the front droop limiters. They are simply cables that prevent the strut from drooping past the point where the spring comes loose. In my case they stop about 1" of droop travel. I have not installed them on the rear because my rear springs do not unload at full droop. The front droop limiters do reduce body roll. Here is some video of the car from an autocross at sebring two weeks ago: I am extremely happy with the way the car is handling, but I still plan to get some bigger wheels before the next set of tires.

I checked my numbers with DG's calculator and came up with LF = 665.31 Lb RF = 621.69 Lb LR = 707.69 Lb RR = 661.31 Lb. These are pretty darn close to my final numbers of LF = 662 Lb RF = 623 Lb LR = 708 Lb RR = 661 Lb.

I corner balanced the car again yesterday. I try to do this whenever I make significant changes. For those of you following along, I completely changed my suspension set-up. I went from 250 rear/ 200 front springs with a 1" front sway bar to 425 rear/450 front springs and an 18 mm front sway bar. The car has also been lowered 1" all around, the stock seats have been replaced with lightweight MOMO Start2007 seats, the rear struts have been sectioned, and rear camber plates installed (all since October). So I thought it was time to rebalance the car. Here are the starting numbers with driver (me) and fuel: LF = 683 Lb RF = 604 Lb LR = 690 Lb RR = 679 Lb. Total = 2656 Lb These were my percentages: (LF + RF)/ Total = (683 + 604)/2656 X 100%= 48.5 percent on the front 51.5 % on the rear. (RF + RR)/ Total = (604 + 679)/2656 X 100% = 51.7 % on left and 48.3% on right. my diagonals were a little off: (LF + RR) = (683 + 679)= 1362 (RF + LR) = (604 +690) = 1294. To fix this, I raised the RF spring perch 1 turn (1/8"), and the LR 1 turn. After this minor adjustment, these were the results: LF = 662 Lb RF = 623 Lb LR = 708 Lb RR = 661 Lb. (LF + RR) = (662 + 661)= 1323 (RF + LR) = (708 +623) = 1331:mrgreen: Here is the thread that discusses all of the suspension stuff that has been performed since October: http://forums.hybridz.org/showthread.php?t=130005 Here are the final numbers with fuel but no driver: LF = 603 Lb RF = 622 Lb LR = 627 Lb RR = 617 Lb. Total = 2469 Lb These were my percentages: (LF + RF)/ Total = (603 + 622)/2469 X 100%= 49.6 percent on the front 50.4 % on the rear. (LF + LR)/ Total = (622 + 617)/2469 X 100% = 49.8 % on left and 50.2% on right.

Those look great! When I get around to making my next set, they will be similarly constructed. The only thing that I plan to do differently is make the rear heim the solid point, and let the front heim be the toe adjuster. What wall tubing did you end up with? My current control arms are made using 1.125 x 0.058 4130 tubing, but they use a lot of extra triangulation for redundancy. With your new control arms you have converted the rear suspension from an H-arm to an A-arm toe link type strut. By doing so, you have given youself more freedom regarding toe and caster. The H-arm type strut suspension demands that the strut is perpendicular to the control arm. If the strut isn't perpendicular, the control arm and strut must flex or bind as the suspension goes through its range of motion. Because of the requirement for an H-arm strut to be always perpendicular to the control arm, caster and toe are limited. The A-arm type gives you more options. You can now move the top of the strut forward or aft. As the suspension moves through its range of motion, the toe link rotate to prevent the suspension from binding. Moving the top of the strut forward or aft will allow you to play with anti-squat and roll steer of the rear suspension.

I think they may be second generation RX7 mirrors. I have been thinking about putting a set on my car.

What Jon said... I made my control arms several years before the threads mentioned above. My control arms are functional and light, but I have to be careful to verify that the bolt going through the outer pivot is not in a bind after a camber or toe adjustment. If I were to make another set, they would be a little different and would incorporate what has been learned during discussion on HybridZ. My new set would look more like Cary's (tube80z). The only thing that I might do different is make the rear rod end fixed in the plane of the control arm and let the front rod end be the toe link. Either way, I can reuse my jig (as can you) with little or no modification.

That is similar to the manner in which I constructed my control arms. Here is a Jig that I made: On my jig, you weld one side of the control arm, then flip the control arm to the other side and then weld the other. One issue that I see with your control arm design is that the axis of the two rod ends are not parallel. As you adjust the length of the rear rod end, the spacing between the rod ends will change. This will create a binding situation between the strut and control arm.

The stock seats are fairly light as stock seats go. In my case however, I autocross the car. I count every pound, and I needed lateral support. I am at the point with my car that finding weight that can easily be removed is difficult. So losing 18 pounds with a pair of lightweight seats was a bonanza.

I just put a pair of MOMO Start2007 seats in my car. They are not a cheap seat, but they are relatively inexpensive. They are FIA approved fiberglass seats that weigh 18.5 lbs each. With the mounting brackets installed, they weighed 23.5 lbs each. The stock 260Z seats weigh 32.5 lbs each, so I was able to lose 18 lbs by installing the two seats in my car. I have had the seats in the car for three autocross events, and really like the comfort. They fit me perfectly but will not work for larger drivers. I am 6'0" and weigh 185 lbs. They are a tight fit in the car. The widest part of the seat at the shoulders just barely clears the door, and the widest part at the knees just barely clears the driveshaft tunnel. Because they are side mount seats, it is possible to mount them very low(which is good for me). They seem like they were made for mounting in the Z car. I bought my seats from LTB motorsports here in florida. He is a local SCCA racer and has an Ebay store. For me, the good part was that he was nearby, so that I could sit in them before I bought them. He sells them for 361.00 each on Ebay with free shipping. If you are local and can pick them up, you can save some money. You will also need the MOMO side mount brackets. This is the only picture that shows the seats at all. I'll have to borrow a camera and get some installation pictures.

I haven't used the ultra-flo X muffler, but thanks for posting. I currently use a pair of old 40 series Flowmaster mufflers. They sound great, but they are heavy. So I am considering replacing the two flowmasters with a single ultra-flo X (somewhere along the tunnel) with mandrel bent tail pipes to the rear. I think the Ultra-Flo X should provide sufficient sound attenuation without additional mufflers down stream (At least for my application: E mod autocrosser).

Thanks for the responses. Jon you are correct, I am neglecting the tire contribution to roll. Also, I lowered my tire pressures for this event. I have previously been running 40 psi front and 36 rear (cold), for this event I lowered the front to 32 and the rear to 28. I am just shooting in the dark until I get a tire pyrometer. That will be my next purchase. Cary, I have been wanting to try droop limiters. My next event is in 2 weeks in Gainesville, Fl (05/18/08). I hope to have droop limiters on the front by that time. From my picture, it appears to me that the inside tires are fully drooped (limited by the struts) and that the outside tires are on the Koni bump rubbers.

Saturday, I finally got the car aligned for the first time since redoing my suspension. Here are the alignment settings that I used: Front: 0 toe, -2.5 degrees camber, and 5.6 degrees caster. Rear: 0.10 degrees toe in, -2.1 degrees camber. Sunday, I ran an autocross and the car did extremely well considering that I have some seriously dead Hoosier A3S04 tires. At the limit, the car had just a little understeer, and the rear traction was much improved from the last couple of events. I attribute this to using less rear camber and less toe in at the rear. There was a photographer present, so I asked him to get some pictures of the car in various parts of the track. The following picture surprized the heck out of me. The picture was taken at the end of a fast sweeper with a decreasing radius exit. The body roll in the picture is about 3 degrees. This is more roll than I expected the car to achieve with the tires and suspension that are in place (Hoosier 245/45/16, 450 lb/in front springs and 425 lb/in rear springs). The weight transfer worksheet predicts 1.6 degrees of roll per gee of lateral acceleration (for a steady state 1 gee turn). I guess I overlooked the additional roll that will occur in transient manuevers. Also from the pictures, it looks as if the rear tires have sufficient camber to compensate for body roll, and it looks like the front tires could use a little more negative camber. Unfortunately, in order to get more negative camber on the front I have to either lengthen the lower control arms or give up a little bit of caster. I will probably make some new lower control arms (and outer tie rods) to widen the front track, and allow me to run more static negative camber. Before I do make new control arms, I plan to do the following to add to this thread: Measure front camber gain. Measure front bump/roll steer.